Lotus Elan

Huco fuel pump

PostPost by: ricarbo » Wed Nov 20, 2013 4:56 pm

If you're fitting it in the boot, another question arises with the Huco. Their details on the Gower & Lee website shows 4 models. 2 for near the tank with a pressure of 4.3 psi which seems too high. 2 for the engine compartment with 2.2.psi which seem more like it. Oddly the two near the tank have identical specs, but the engine compartment ones are different voltage. I suspect there is a typo for the near the tank models and there are different voltage versions, but it does need clarifying. Also, the pressure in a static liquid is a constant, unless things have changed since I was at school, so the 4.3 psi will appear at the carbs when the float valves are shut. The pressure may well be less when the float valves are open and maybe that is why they propose a higher pressure version when fitted near the tank. But it would help if they would explain why different pressure versions are specified for different locations. I would have thought the low pressure version is correct wherever it is fitted.
So that's two questions that need to be answered, no, hang on, three! Their flow conversion table says 12 litres/hr is the same as 26 gallons/ hr. I think they meant 120 litres/hr.
Maybe their typist was having a bad day. What's a mebrane?
I imagine 26 gallons/hr is a very plentiful rate for a car that does 30 mpg, but I have no idea as fuel is obviously not used at a steady rate and the pump needs to pretty much keep up with the peak rate.
regards
Richard
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PostPost by: Quart Meg Miles » Thu Nov 21, 2013 1:07 pm

ricarbo wrote:.... the Gower & Lee website shows 4 models. 2 for near the tank with a pressure of 4.3 psi which seems too high. 2 for the engine compartment with 2.2.psi which seem more like it.

..... the pressure in a static liquid is a constant, unless things have changed since I was at school, so the 4.3 psi will appear at the carbs when the float valves are shut.
Richard

I think scuba divers would disagree as every 30 feet they descend increases the water pressure by one atmosphere i.e.14.7 psi. The Huco isn't intended just for small cars like the Elan and the carburettors in some vehicles might be a couple of feet higher than the installed pump, requiring an extra pound or two pressure to raise the fuel.

If you have a pressure gauge fit a bit of hosepipe full of water to it, raise the end and watch the pressure go up.
Meg

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PostPost by: billwill » Thu Nov 21, 2013 3:42 pm

Just to have all the relevant info in this one thread, here is the circuit that I suggested some time ago for fuel pump switch off by oil pressure:

Image

From thread
lotus-carbs-f40/electric-fuel-pump-noisy-idle-t20354-15.html#p117904


It works as follows.

When ignition is off oil pressure is low and oil pressure switch is closed.
As soon as you turn ignition on, oil pressure starts low.
The relay closes This OPENS the connection to the fuel pump so it doesn't run.

If the engine starts with the existing fuel in the carbs, all OK
    Otherwise press and hold the priming button until the carbs are full & the fuel pump is just ticking.
    Release button
Start engine
Oil pressure now opens the oil pressure switch

The relay opens, which CLOSES the connection to the fuel pump, so with oil pressure present the fuel pump runs as normal.

If the engine stops (in a crash etc) the oil pressure drops, the oil warning switch closes, which turn ON the relay, which turns OFF the pump.
Bill Williams

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PostPost by: ricarbo » Thu Nov 21, 2013 5:12 pm

Yes QMM, you're right, of course, but I chose to ignore that bit because I expect the height of the fuel pump would be so similar as to make no practical difference, whichever end of the car it is fitted. I didn't want to cloud the issue. If the difference was 1 foot, the difference would be about 0.28psi, I think, given the specific gravity of petrol is around 0.7 that of water. Perhaps I should have said, as long as the two ends of the pipe are at the same height, then the static pressure will be the same at each end.
Regards
Richard.
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